(a) Field of the Invention
The present invention relates to a thin film transistor array panel and a liquid crystal display including the same.
(b) Description of the Related Art
A flat panel display is a display device in which the depth of the display is relatively thin as compared with the size of the screen. Liquid crystal displays (LCD), plasma display panels (PDP), and organic light emitting devices (OLED) are types of widely used flat panel displays.
The LCD is a display device that utilizes electro-optical characteristics of liquid crystals. In an LCD, the amount of light transmitted through the liquid crystal is varied according to the intensity of an applied electric field and thereby images are displayed. The PDP is a display device in which plasma generated by gas discharge is used to display images. In the OLED, electrons and holes are injected into an organic illumination layer respectively from a cathode (the electron injection electrode) and an anode (the hole injection electrode). The injected electrons and holes are combined to generate excitons, which illuminate when converting from an excited state to a ground state, and thereby display an image.
A structure of a flat panel display in which the thin film transistor and the color filter are formed on the same substrate is referred to as “color filter on array” (COA), and a capping layer is generally formed on the color filter in the COA structure. The capping layer prevents the color filter from lifting or separating from the substrate. Generally, the color filter is made of an organic layer that has some degree of elasticity. The capping layer, however, is made of an inorganic layer and has small elasticity and compression compared with the color filter of the organic layer. Accordingly, when forming the solid capping layer on the smooth color filter, significant stress is generated in the capping layer.
Also, gasses such as H2 and N2 may not discharge to the outside of the device, and thus remain between the capping layer and the color filter. When such gasses collect between the capping layer and the color filter, cracks may be easily generated near a contact hole for connecting the thin film transistor and the pixel electrode. Such cracks are usually a result of applied heat or an impact to the device. When such cracks occur after the device has been filled with the liquid crystal layer, the gas may outflow through cracks into the liquid crystal layer, and then bubbles are generated such that an active unfilled area (AUA) defect appears. Such an AUA defect can cause light leakage.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.